SIDS has been the leading cause of death for infants aged one month to one year in the United States for the past two decades, with more than 5,000 SIDS deaths occurring annually prior to 1992. Since 1992 the "Reduce the Risks" public health campaign, together with the U.S. Public Health Service "Back to Sleep" campaign beginning in 1994, has been associated with at least a 40% reduction in SIDS mortality rates in the U.S. This past year, we published results with other colleagues on the progress achieved since 1992 in changing infant sleep position in the U.S. Based on the annual surveys conducted for the National Infant Sleep Position (NISP) study, we have shown that the prevalence of placed prone (on stomach) to sleep of infants under 7 months of age in the U.S. declined 66% between 1992 and 1996. Also, we have compared the changing profile of epidemiologic risk factors for SIDS, among high and low risk infants, over the past decade in the U.S. Besides changing infant sleep position from stomach to side or back, there remain many other important, potentially modifiable risk factors for SIDS. These national data indicate the importance of young maternal age and relatively high parity as continuing factors increasing SIDS risk, after adjustment for several other known risk factors. We have also examined trends in maternal smoking, which is also a strong risk factor for SIDS both in the U.S. and other developed countries. We completed analyses for a study of low birth weight infants, many of whom were sent home from the hospital with apnea monitors. All of the children in this case-control study were followed-up at approximately 18 months of age with the Denver II Developmental Screening Exam. None of the monitored infants died. The infants sent home from the newborn nursery with apnea monitors, however, differed from birth weight-matched control infants on several of the Denver II developmental domains, including gross and fine motor development and speech/language development. In addition, we have collaborated on the Chicago SIDS/Infant Mortality Study and completed analysis of a substudy, which examined laryngeal basement membrane thickening in infants dying of SIDS or of known causes. Contrary to prior published results, SIDS infants in the Chicago study were not more likely to have laryngeal basement membrane thickening. Also, we have participated with researchers at Allegheny University conducting a PCR study of infections in SIDS cases and control infants.